Your Blood In My Veins
by KassandraScarlett
Summary: Dean makes Sam drink his blood. It backfires pretty spectacularly. (Demon!Dean, King Of Hell!Sam{kind of}, Cross-posted on AO3)


"Sam, come on," Dean sighed. He was starting to sound exasperated and if Sam tried, he could pretend it was his brother teasing him about being such a nerd. "For _once_ in your life, stop rebelling and listen to me. I don't wanna be cured. I'm happy this way."

"No, you _think_ you're happy," Sam corrected. "But you're not exactly you right now. So, yeah, trust me, if you were yourself, you'd wanna be cured."

Dean laughed disbelievingly. "Are you deluded? Have you been hearing a word I've said? Or did I accidentally do something to make you think I appreciate being repeatedly jabbed with a needle?"

Sam kept his eyes on his watch, counting down the last few minutes left till the next hit.

But at Dean's words, he looked up, sharply. "Yeah, actually, you did. You left me alive."

Dean raised an eye brow. "Are you punishing me for sparing your life?" He asked dryly.

Sam pushed off the table to stand upright. "You've known me my whole life. You _know_ how I am, you know what makes me tick. You can't seriously tell me that you expected me to just '_let you go_', can you?" He didn't bother hiding his skepticism. "You _must_ have known I wouldn't give a crap about that note. You must have known that at some point, I'd catch up to you. So why didn't you kill me?"

He wasn't sure when he'd stepped forward, but he was kneeling in front of Dean, syringe ready in his hand. "No way you missed the empty bottle of Jack on your way out the door. I was drunk, miserable, and desperate. I would have hugged you before wondering how you were alive. It would have been child's play to stick a blade in me. So why. Didn't. You? _Why leave me alive_?"

Dean didn't answer, just glared back. Sam sighed. "I think it means that either there's a small part of you that's still my brother, that wants to be saved. Or you've got an ulterior motive I can't see yet."

And Dean was a good liar, but Sam had it down to an art form. So, while he'd been mostly bluffing, the defiant raise of Dean's chin told him he'd accidentally guessed right.

But there was nothing else he'd get Dean to fess up. So, remembering how Crowley had bit his hand, Sam moved to stand behind the chair and used his useless hand to yank at Dean's longer hair, forcing him to expose his neck so he could inject the blood.

The furious growl of pain that escaped Dean made Sam's heart clench. He didn't want to hurt him. But what choice did he have?

Moving with the instinct to comfort his brother, Sam cupped the side of Dean's face in one palm, as Dean tried to catch his breath. He patted his cheek once, twice, the way he did whenever they hugged, before moving back to the table to wait for the next hour.

* * *

Dean had had a plan. Let Sam stew in his loneliness and despair for a few months. When he was desperate enough for any small part of his brother, Dean would swoop in, fess up to being a demon. Show how well-behaved he'd been, not hurting any humans (_except the ones who deserved it_), only other demons. Sam would have been so glad to have him back, he would have accepted Dean in any way, shape or form.

But Dean had slipped up. He'd let himself get caught on camera in that one Gas n' Sip. And Sammy had always been ridiculously keen-eyed. He must have spotted the flash of black in Dean's eyes. So Sam had found out way too early for his plans.

And then, Crowley had let himself get played, and Sam had traced them. And after that, Crowley had given him up. Spineless son of a witch.

Which is why, now, Dean had to make a small improvisation. He had to come clean to Sam and hope that it was enough, that Sam would see reason. Otherwise, Dean was screwed.

"Didn't I tell you you're too smart for your own good?" Dean began.

Sam looked up from his book (_he was reading while he had a Knight of Hell locked up; was his little brother actually suicidal?_) and raised a curious brow. "No, actually, you've told me to stop being a smartass," he replied calmly.

Dean smiled, letting his tongue curl over itself. "So, maybe you were right, Sammy. I had plans for you. For us. That's why I left you alive. Though in my defense, I hoped it would take you a few months to find out I was a demon and a few more before actually finding me. You threw a wrench in my plans, but I gotta say, well done. I'm kinda proud of ya, little brother."

Sam sighed, closing the book. "Cut the crap, Dean. Are you going to tell me these plans of yours?"

Dean decided to be blunt about it. "I want you to rule hell."

Sam blinked, then scoffed. "Is that the best you can come up with?"

"Crowley is useless," Dean cut in. "And he thinks he can order me around. But Knights of Hell are loyal to only the King. Not the self-proclaimed one, either. Why do you think he and Meg had beef, huh?" He questioned. "Because Meg was Azazel's daughter. She was the true heir to the throne. Except she wasn't alone." Dean smirked, when Sam's widened in realization. "Azazel had named you his first heir. Crowley just never saw you as a threat because you weren't interested obviously. Neither did Meg think of you as competition. But now with Meg gone? You're the sole heir. And I'm willing to bet even Abaddon felt the same way I did. She just decided the same thing as Meg and Crowley- so she decided to take over instead."

"What do you mean, same way you feel?" Sam asked. "What do you feel?"

"Your claim to the throne," Dean answered smugly. "Like I said, Knights serve the King. I can sense the connection between you and Hell. It's dormant, which is why you can't feel it, but I can. You're the rightful King and if you take your throne, I'll happily pledge loyalty to you."

Sam stared for a few seconds. Then he laughed, sounding slightly strangled. "Loyalty?" He repeated sarcastically. "Dean, you're a demon."

"So was Ruby," Dean reminded. "But she loved you. Why do you think I hated her so much? So was Meg, but she loved Castiel. Crowley loves his son. Is it so hard to believe that I still love you, Sammy?"

Sam actually cringed. "You never say stuff like that."

Dean waved his hand flippantly, as well as he could while tied up. "I'm a demon, like you pointed out. I don't exactly worry about stuff like what sounds too sappy and what's the right amount of masculinity. I'll say whatever is on my mind." It was true. Even as demon, he couldn't stop caring about Sam. It was just part of who he was.

Sam shook his head. "I can't believe I'm actually listening to this," he muttered, brushing his hair away. "I'm almost flattered, Dean, but I'll take a pass."

"Think about it, though, Sam," Dean implored. "You could remake Hell however you want it to be. You'd get to choose which deals are valid, who deserves to lose their souls and who doesn't. You'd get to decide what punishments are befitting for which kind of people."

Sam shook his head and began to gather up a needle. Dean began to panic. Fuck, he wasn't sure he could take another hit of blood without passing out.

"We'll be immortal. Won't need to worry about anybody messing with us. Nobody would dare to challenge you, not with your connection to Azazel and Lucifer, not with the powers you have. We'd be free."

Sam acted like hadn't heard a word Dean had said.

"I'm offering you my blood, Sam," Dean snapped.

To his relief, Sam froze, shock and apprehension coloring his features. "_What_?" His voice had dropped down to a low register, gritty and threatening.

Dean resisted a shiver. "I'll give you my blood. However much you need. And who knows, Knight blood is probably hell of a lot tastier than any run of the mill demon."

Sam shook his head. "You're crazy," he protested, hoarse and shocked. "Dean would _never_ even _think_ of something like this."

"Maybe, maybe not," Dean agreed. "But you were once willing to live as immortal zombies just so we could spend eternity together. You telling me you don't love big brother that much any more?"

"Why are you doing this?" Sam asked, demanding. "What's in this for you?And don't tell me it's because you want to serve the 'true king' or whatever. What's your advantage?"

Sam was at eye-level now and Dean made sure not to break eye contact. "Tell me something, Sammy," he crooned. "Were you actually attracted to Ruby? Or did drinking demon blood make you horny?"

Sam looked confused.

"Because you said Ruby reminded you of me," Dean reminded. "And if that's true, and you fucked her, what does that mean for us, huh, Sammy?"

Sam stilled, his face blank.

"You know your old brother liked to delude himself," Dean went on. "He thought he couldn't have you. He kept you on a freaking pedestal. But he never denied he wanted you. He wanted you when you ditched his ass for Stanford. He wanted you when you were crazy and seeing Lucifer. He even wanted you when you were shacking up with that girl and a dog. He felt dirty, wrong, fucked up in ten more different ways than you. But I know better." He leaned forward. "If what you said about Ruby was true, then you want me too. You want to hold me down and do all sorts of filthy things to me. Or it was the demon blood." And for all his bravado, the foreign blood in his body made Dean feel just human enough to admit that if he only got to have the rest of Sam because of the blood, it would break his heart a little. He wanted, really wanted, Sam to willingly choose him. But he'd take what he could get. "Either way, I get what I want. So..." He tilted his head back, exposing his throat. "Take a bite, Sammy. You get to have power and you get to be with me forever, just like you wanted. And I get to fulfill every fantasy I've had since I was 19."

For several long seconds, neither of them moved. Dean could feel Sam's eyes on him, could almost hear him, calculating. A large, warm hand landed on the side of his neck, calloused thumb rubbing a circle right over his pulse.

For a wild moment, he thought Sam would actually take him up on his offer. He was sure of it, could see Sam lean an infinitesimal inch forward, and his whole body was tingling with the anticipation of Sam's teeth on his delicate skin.

But the hope was shattered as the needle jammed into him, Sam's blood lighting up his insides like 4th of July fireworks.

As he finally lost consciousness, dimly aware of Sam's retreating footsteps, he wondered if all demons felt heartache.

* * *

Sam should have known. He should have known that no matter what Dean had said about still loving him, wanting him (_and that was a can of worms he wasn't about to inspect just yet_), and wanting to serve him as king, Dean was still a demon. And demons took what they wanted.

No matter how or what Dean had said while bound and restrained, he was free now to force himself on Sam. And Sam... Sam would be lying if he said there wasn't a part of him that was tempted.

Dean had gotten that part right. Sam had been wanting Dean in all the ways he shouldn't since he'd hit puberty. And the idea of remaking Hell? Locking all demons inside without having to actually shut the gates? Enticing. But it was all too much, all too wrong. And Sam didn't care about his own soul. He never really had, not since Lucifer had declared his claim on it.

But he'd rather do the Trials again, than allow Dean's soul to be twisted any more. Dean had suffered enough.

All these thoughts ran through his head as Dean finally quieted down, his taunting remarks and cajoling coming to a stop.

Sam tensed. The silence could only mean that Dean was closer.

Knife in one hand, bad arm useless in his sling, Sam edged away from the corner and turned to creep down the hall.

He felt Dean's movement before he saw him. The air in front of his face moved, fast and sudden, and Sam ducked, standing in the very next second to place the knife at Dean's throat.

Dean actually smirked, half proud and half challenging. He let go of the hammer now lodged into the wall.

"Well, look at you," he drawled. His lips gleamed pink and Dean knew it, that fucker, letting the tip of his tongue tease the corner of his mouth. "Do it. It's all you." He spread his arms wide, waiting for Sam.

But Sam could do nothing but stare. His hand was steady, not even a hint of a tremor, but he couldn't move. Couldn't slide the blade across the vein, couldn't bring himself to cut the skin, be it shallow enough to just drink from or deep enough to kill.

He didn't know what to do. And Cas wasn't coming. Where the hell was that angel when he was needed?

"Come on, Sam. Grow a pair and do it," Dean murmured.

Sam felt like smacking himself. Dean wasn't afraid. Not purely because he knew Sam wouldn't go through with it. But because... "The blade won't work on you," he realized. Stupid! They'd used it on Abaddon, it hadn't left a scratch.

Dean's smugness grew. "Getting slow, Sammy," he purred.

Sam didn't have time to react before Dean was disarming him. He found himself pushed back against the wall, Dean's arm pressing against his neck.

"Don't think we'll be needing this." He tossed the knife away.

"Dean, please," Sam tried to say, his voice choked and strained.

"Shh." Dean leaned up, his lips ghosting over the corner of Sam's mouth. "I warned you. I told you I wasn't going to show you any mercy." Without warning, he kissed Sam.

Sam shuddered, breath sticking in his chest, as Dean's sinful lips pressed against his. He closed his eyes tightly. Somehow, he knew that Dean had bit his tongue and was just waiting for Sam to open his mouth so he would have no choice but to drink. So he kept his lips sealed, stubbornly, even as his heart clenched painfully at the frustrated growl from his brother.

"Come on, Sam," Dean broke away to groan. He slipped a hand between them and gripped Sam's cock through his jeans. He gave a squeeze and Sam moaned, knees nearly buckling as Dean's heat bled through every layer of clothing he had on.

He almost opened his mouth then, almost, but Winchester obstinacy was an inherited trait.

Then Dean pressed a finger into the hollow of Sam's throat, making him choke, and Sam couldn't keep this up forever, because he _needed to breathe_, god damn it, and-

Abruptly, he remembered something Bobby had told him, years ago during the first apocalypse, something that Dean had said to Bobby during Sam's initial detox.

_I'd die for him in a second, but I'd rather kill him myself than let him turn himself into a monster._

And that was what had to happen now, San realized. Because the Dean of this moment was just as much of a monster as Sam had twice been. Because just like Sam, the real Dean would loathe himself in this instant.

And Sam had to save him. Whether he did that by curing the demon or killing his brother- that was up to fate and luck, because Sam had never tried this before.

But either way, he was going to save him. And if he accidentally turned himself into a monster to do so, that was okay too.

So, with a sudden clarity, Sam parted his lips and slipped his tongue into Dean's bleeding mouth.

His eyes rolled back at the first taste. Thick, sweet-and-sour warmth filled his mouth. Dean seemed to gasp, renewing the kiss with increased enthusiasm. There was a small part of Sam that wondered about that. What if Dean really wanted this? What if...?

But he couldn't think about that. Not when he could feel the sulphuric tang moving through his veins, the magnetic tingle in his palms, the rush of pure power. His senses were growing sharper with every swallow. Even with his eyes closed, he was increasingly aware of a heart beating too fast against his own chest, the "_Sammy_" whispered too lightly for normal ears, almost tender and sweet.

Dean's hands released their hold and moved to grip his hair and Sam used his one arm to wind around his waist, pulling him closer. He bit Dean's lips, and his tongue again, because he needed to feel that blood, needed to taste the pure energy flooding him-

Dean shuddered.

And Sam pushed him away.

"What?" Dean gasped. His eyes were tar-black, his lips and teeth and chin stained red. "Sammy, what's- come on, don't freak out on me now, little brother. Just a little bit more, just to be sure, and then we can go hunt Crowley-"

"No."

Dean paused. "_No_?"

Sam was breathing harshly. He felt light headed, energy humming through him. His fingers flexed. Dean's blood was wet around his mouth and he licked his lips. He never took his eyes off Dean. He could see the demon now. Could see the rotting flesh, cheeks hollowed out to reveal bone, eyes sunken and eyelids scorched, hair missing in chunks, everything pulsing lightly with the energy of Dean's true soul. It was like Hell was superimposed over Dean's face and all Sam had to do was scrub it out.

So he raised a hand, palm facing Dean, praying it would work.

"Sam, _no_!" Dean warned, anger and fear in his voice. "No, don't you _dare_, Sam, don't you dare-"

He was flung back against the wall behind him.

Sam advanced. "I've told you before, Dean," he said slowly, curling his fingers.

Dean sucked in a sharp breath, head falling back.

"You're one of the smartest people I know," Sam continued. "But sometimes... Sometimes, you get cocky. And then you don't think things through." He focused on the layer of Hell, folding phantom fingers around the ruined flesh and pulled.

Dean screamed, back arching off the wall. Orange flickered under skin like lightning.

Sam's vision was tinted red. He imagined digging his fingers into Dean's soul, yanking out the infection bit by bit, as Dean writhed under his mental ministrations.

"_No_," he moaned. "No. Sam, _don't_... Sam, _Sammy_, _stop_. Please, Sam, _please_."

Sam tuned it out, even the ruffle of wings and the small sound of surprise as Castiel appeared and took in the scene. He could see it beginning it work, Dean's body growing weaker as the twisted parts of his soul struggled for freedoms from Sam's hold. It was like watching light and darkness fighting each other, struggling for dominance and Sam couldn't bolster the light, couldn't risk touching the pure soul for fear of sullying it, but he could siphon away the demon. He was.

He kept pulling, kept cleaning, until without warning, it gave up. The darkness shrank, receding away into Dean's arm, where the Mark glowed, red and angry, furious at being thwarted. Sam stopped, freezing.

Dean was still, _too_ still. Sam let his head drop, and Dean slid down the wall, limp and boneless.

Sam stared. Was he... No. No, he was fine. He had to be fine. _Please, please, be okay. Don't let this be what kills you. Don't let _me_ have killed you._

Cas kneeled beside Dean, fingers searching for a pulse. Sam had to hold back an instinctual growl. Demon blood woke his darker nature and to see an angel, one without wings or proper Grace and too weak to be of any use, touching _his_ brother, _his_ Dean-

"He's alright," Cas whispered. "He's weak, but he's alright. He'll wake up in a few hours or so."

Sam came to his senses. He leaned back against the wall, muscles relaxing, realizing what vile thoughts he'd been having. His cursed blood, powered up and jubilant, was bringing out the worst in him, like it always had. He was dangerous, right now.

"Cas," he called weakly. He ached to approach Dean, but there was no way he was touching him while he had poison in his veins.

Cas looked up at him, eyes filled with respect, pity and something that looked like awe. Or was it fear?

"I need... I... Cas..." Sam took a deep breath, trying to steady himself, trying to ignore the little voice in his mind that said kill, kill, kill, take what's yours, claim it. "You need to lock me up. Dungeon. Use the cuffs, devil's trap, holy oil, whatever you can think of. We can't be too sure."

"Surely, not all if that would be necessary," Castiel tried to reason. "Just being locked up would be-"

"No!" Sam shook his head. "Dean was saying something about Knight of Hell blood being more potent. He was right. I feel like... Like, I drained ten demons, not one. Like when I'd had to drink to prepare for hosting Lucifer. Cas," he was begging now, he knew it. He just didn't have it in him to care. "Please. You have to do it."

Cas gazed sadly back at him and nodded. Sam could only sigh in relief.

* * *

Dean woke eight hours later. His eyes searched for Sam first, too many thoughts running across his mind that he needed to talk to Sam about. But when he couldn't find his brother anywhere, he looked at Castiel and tried not to panic.

"You look worried," he tried to joke.

"How are you feeling, Dean?" Cas asked gently.

The real question was how was Sam feeling, because Dean had hurt him, violated him, forced demon blood onto him and had said a bunch of stuff that made him want to cut his own tongue out. "I'm fine," he said instead. "I'm okay, I feel... Well, a little weak, sure, but nothing some TLC won't fix. But, uh..." He cleared his throat. "Where's Sam? Is he, uh... Preparing the divorce papers?" He chuckled weakly, even as his words brought back the memory of Sam kissing him. Though he had to admit to some pride that Sammy had played him so flawlessly. He'd kissed Dean, drank his blood, and Dean had succumbed to the ecstasy of it.

"No, Dean," Cas said quietly.

Dean felt a flare of panic. "What?" He asked in a whisper. Sam was fine, he had to be, he told himself. Dean had been careful not to hurt him, not to draw even an ounce of blood. Had he gone then? Had he left? Too disgusted by Dean's sick desires?

"He's in the dungeon," Cas finished. "Voluntarily. He said detox was too risky to be done under any conditions except lock and key."

Dean wasn't sure if that was better or worse. For one thing, at least Sam hadn't left him (yet), which meant the situation could maybe still be salvaged if Dean chose his words right. On the other hand, detox was its own brand of torture and Sam's head was not somewhere Dean wanted him to be stuck in.

"And you're here with me?! " He exclaimed.

Cas blinked.

"You can't leave Sam alone while he's detoxing," Dean nearly yelled, stumbling out of his bed. "That kid is too smart to be left on his own, he'll torture himself to death in there, he knows exactly how to do it, and he could be calling for help. Dammit, Cas, all you had to do was stay near the door, and let him know he wasn't alone!" In the back of his mind, as he raced unsteadily down the hall, Dean dimly thought Cas had sighed almost fondly, muttering something that sounded like "_It's a wonder you two haven't glued yourselves together more literally._"

But his thoughts were mainly on his little brother and as he reached the dungeon, the screams reached his ear and his heart stopped.

"_NO_!" Sam sobbed, his words clear even through the thick doors. "No, _Dean_, PLEASE, I'm _sorry_. _Don't say that_. Not again, I won't do it again, _I'm sorry. DEAN!_"

Dean bit back a sob. He placed a hand on the metal door, knowing that going in now would only confuse Sam more. So, he just rested his head against the door, saying, "I'm here, Sammy. I'm right here, kiddo. It's okay. I'm not leaving you. I'm not going anywhere." It was a promise he intended to keep.

He wasn't sure if Sam's sobs quieted because he could hear Dean's words, or because the hallucinations had decided to give him a break. Either way, he wasn't about to move from here too soon.

Mostly impatient for Sam's ordeal to be over, a little apprehensive of the conversation they were sure to be having, Dean sat on the floor, back resting against the door, listening to Sam's quiet pleas, with only the memory of Sam's soft lips to keep him company.


End file.
